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    <script>

         //var声明的同一个变量在同一个作用域中可以多次声明
        var email = 'lisi@qq.com';

        var email = 'zhangsan@sohu.com';
        console.log(email);


         //let声明的同一个变量在同一个作用域中不能重复声明
        let age = 20;
        age = 18;   //使用变量age
       // let age = 18;  //'age' has already been declared

        console.log(age,'age');

    </script>
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